Self-locking nut



M. BELTOISE Oct. 1, 1968 SELF-LOCKING NUT Original Filed Jan. 2, 1964 5v: m E M M E a VW T wL/m E B/F m 6 M5 M M United States Patent 26,469SELF-LOCKING NUT Maurice Beltoise, Paris, France, assignor to Beltoise,Marquet 8: Co., Paris, France, a French society Original No. 3,198,229,dated Aug. 3, 1965, Ser. No. 335,123, Jan. 2, 1964. Application forreissue Aug. 9, 1966, Ser. No. 573,158

4 Claims. (Cl. 151-21] Matter enclosed in heavy brackets appears in theoriginal patent but forms no part of this reissue specification; matterprinted in italics indicates the additions made by reissue.

The present application is a continuation-in-part of copendingapplication Serial No. 86,056, filed January 31, 1961 and now abandoned.

This invention relates to self-locking nuts of the deformable type inwhich, simultaneously with the selflocking action, the bearing end faceof the nut is adapted for self-alignment into a plane parallel with thebearing surface against which the nut is screwed.

To achieve the simultaneous self-locking and self-aligning effects, nutsof the type to which the invention relates generally include an innercylindrical part or bushing which is internally threaded to constitutethe nut proper, and a coaxial outer skirt part which is connected withthe inner part by an annular wall or web portion generally normal to theaxis of the nut, and positioned at the end remote from the bearingend-face of the nut. This connecting web is deformable, and as the nutis tightened down against a bearing surface the bushing and skirt aresubjected to a substantial relative displacement through deformation ofthe connecting web, and in so doing provide the desired self-locking andaligning actions.

In self-locking nuts of this type high local stresses are set up in thecomparatively thin and flexible connecting web during the tighteningstep, and this has frequently resulted in the appearance of small cracksor internal tensions within said web which in turn have led to a rapidbreakdown of the nut under the vibrational and shock conditionsencountered in service. To overcome this difliculty, it has beenproposed to provide a separate ring member or insert interposed in theannular space between the bushing and skirt portions of the nut at theend thereof adjacent to the bearing surface, and serving to transmitforces directly between the bushing and skirt while not preventing therequisite relative displacements therebetween. The ring insert has, ineffect, served to transfer the deformation stresses arising during thetightening of the inner bushing of the nut against the bearing surface,to the surrounding skirt which is much stronger and better able to takeup the resulting strains than is the deformable connecting web, and thisexpedient has been generally successful in prolonging the service lifeof the nut. However, the necessity of providing this annular insertwhich has to be separately machined to a special contour with ratherclose tolerances, has increased the cost of the self-locking nut devicesand has made them more complicated and inconvenient to utilize.

It is an object of this invention to provide an improved construction ofself-locking, self-aligning nut devices which will be completely freefrom the difficulties and drawbacks just described. Objects are toprovide such nut devices which will be of integral one-piececonstruction so that they will be simple and inexpensive to make andhandy to use, while yet being so designed that the high internalstresses generated during the nut-tightening step will be effectivelydistributed throughout the nut sructure rather than being localized inthe connecting web, thereby insuring prolonged service life understrenuous vibrations and shocks.

"ice

Briefly, in accordance with the invention, a self-locking nut comprisesan internally-threaded inner bushing portion constituting the nutproper, an outer skirt portion coaxially surrounding the bushing portionand connected thereto by way of a annular web at the end of the nutremote from the bearing end of the nut, [at least one of] said bushingand skirt portions being [so contoured that their outer and innerperipheries, respectively, are] in mutual engagement over a substantialaxial length adjacent to said bearing end of the nut. The engagementbetween the bushing and skirt portions is such as to insure substantialtransfer of stresses between said portions, while not interfering withthe necessary relative sliding displacements therebetween.

In a preferred form of the invention, the mutual peripheral engagementbetween the bushing and skirt portions adjacent the bearing end of thenut is obtained by forming the bushing portion with an outwardlyprojecting or thickened contour adjacent said bearing end.

An exemplary embodiment of the invention will now be described forpurposes of illustration but not of limitation with reference to theaccompanying drawings, wherein:

FIG. 1 is a plan view of an embodiment of the improved nut device.

FIG. 2 is a cut-away perspective view thereof, the cut being made on theplanes IIII of FIG. 1, and

FIGS. 3 and 4 are axial sectional views of the nut device in operativeposition around a bolt, respectively before and after the nut has beenscrewed home against a bearing surface.

As shown in FIGS. 1 and 2, an improved self-locking nut comprises anintegral structure including an inner nut portion or bushing 1 which isinternally threaded, and an outer or skirt portion 2 which eoaxiallysurrounds the bushing. The bushing and skirt portions are integrallyinterconnected by a generally radial annular wall or web 3 at one end ofthe nut structure. The skirt portion 2 is shown contoured to provide theconventional hexagonal form; however any other desired contour e.g.cvlindrieal may be used. The end face 2a of the skirt 2 remote from theconnecting Web 3 constitutes a surface adapted to be tightened against aflat bearing surface as will presently be described.

In accordance with the invention, the 'bushing portion 1 has its outerperiphery so contoured as to form an enlargement 1a which engages theinner periphery of the skirt over a substantial axial area exte dingfrom the free end of the bushing. As shown in FIGS. 1 and 2, the axiallength of said area is indicated as h, while the transverse width of thearea of contact engagement between the bushing periphery and each of thesix fiat sides of the hexagonal skirt is indicated as l. The respectivevalues of the h and 1 dimensions may vary considerablv depending on theprecise shape of the nut and the particular production method used inits manufacture. Should the inner periphery 2b of the skirt portion becylindrical rather than hexa onal as shown, the area of engagementbetween the bushing and skirt would extend continuously around thebushing. rather than being limited to only a portion l of each of theflat sides thereof as is the case in the illustrated example. [In anycase'l Ar shown. the axial extent h of the area of en agement [shouldbe'l is substantially less than the full free length of the bushing,[c.g. half said free length or less] so as to leave an annular space 4between the bushing and skirt portions adjacent the connecting wall 3.

As shown, the skirt portion extends beyond the nut portion at the endremote from the connecting web, in the relaxed or free condition of thenut. In FIG. 3, the amount by which the skirt projects beyond thebushing is indicated as the length t. Also, in the relaxed or loosecondition of the nut the bearing surfaces 1b and 2c of the bushing andskirt respectively do not lie fiat and parallel to the bearing surface,but rather are somewhat coniea], or tapered, such that said bushing andskirt will first engage the bearing surface, during the screwingoperation, along circumferential ridge lines 1c and 2d respectively,which constitute the radially innermost lines of the end surfaces 1b and2c of the bushing and skirt; this relationship is clearly apparent fromFIG. 3.

In use, the nut is mounted on a bolt or screw rod with the free ends ofthe bushing and skirt portions, i.e. the ends remote from connecting web3, directed towards the bearing surface, here the surface of a flatframe memher 6 against which the nut is to be screwed. FIG. 3 shows thenut in the position where the projecting inner circular rim 2d of theskirt portion is just touching the bearing surface; the nut is stillsubstantially in its free or relaxed, undeformed, condition. As furthertorque is applied to rotate the nut beyond this position, the bushingportion 1 is forced downwards (as shown by arrow F, FIG. 4) relativelyto the skirt 2 which is blocked against movement, such relativedisplacement being made possible by the deformability of the connectingweb portion 3. Owing to the resistance opposed to the downwarddisplacement of the threaded bushing portion 1 by the skirt 2 at thisstage, the contact engagement between the threads 7 and 5a of the nutand bolt occurs along the upper surfaces of the nut threads, as is shownin somewhat exaggerated :form in FIG. 3. Due mainly to the taper of thefree edge surfaces 1b and 2c of the bushing and skirt, however, thethreads 7 of the nut tend to penetrate deeper into the screw threads 5aof the bolt as securing proceeds, so that ultimately in the fullyscrewed condition of the assembly shown in FIG. 4 the contact engagementbetween the threads is substantiallly equal as between the two sides ofeach thread. Thus the desired self-locking (and self-aligning) actionsare achieved.

In the ultimate stages of the screwing process, considerable stressesare generated in the nut material, due partly to the afore-mentionedpenetration and radial clamping of the threads of the nut inwards intoand around the threads of the bolt. In prior self-locking nuts in whichthe adjacent peripheral surfaces of the bushing 1 and the skirt 2 wereradially spaced from each other at their free ends near the bearingsurface, these stresses were mainly or exclusively transferred to thedeformable web portion 3 and there tended to set up dangerously highstrains resulting in premature breakage. However, in the constructionhere described the said stresses are effectively transferred between thebushing and skirt portions 1 and 2 by way of the interengaging areas atthe base of said portions, whereby the strains are evenly distributedthroughout the bushing and skirt portions rather than being localizedchiefly at the relatively weak annular web at the top thereof. In thisway the useful life of the nut is greatly extended. At the same time thesaid engagement does not interfere with the relative axial slidingdisplacement between the nut and skirt during screwing operations.

In case of an axial expansion or elongation of the bolt 5 with which thenut is used, the bushing 1 is displaced axially upwards relative to theskirt 2 as shown by arrow F1 in FIG. 4, so that said elongation is takenup by the deformation of the nut structure while retaining properinterlocking engagement between the threads. Also in this case anystresses generated by such deformations are transmitted to the skirtdirectly through the interengaging areas at the base of the nut, norwill they tend to set up dangerously concentrated strains in the web.

The improved self-locking nut of the invention is simple and inexpensiveto manufacture, as from a press-formed or upset blank, since it does notrequire a separately machined annular insert as in the earlier typementioned above, and for the same reason is more practical to use.

The precise shape of the upper portion of the nut defining thedeformable web may be readily determined so as to impart the desiredflexibility, and while the precise configuration may vary widely, as byvarying the angles a and a1 and the radius b shown in FIG. 4, onesatisfactory configuration is substantially that shown in the drawings.

Various other changes and modifications in shape and relativedimensioning may be made without departing from the scope of theinvention. Thus, in the undeformed or relaxed condition of the nut, thebushing and skirt surfaces need not be in actual engagement but may beslightly spaced from each other, and the contact engagement between themmay first occur only after some preliminary deformation has beenimparted to the nut during the screwing process. Further, the positionaland dimensional relationship between the free ends of the bushing andskirt, as well as the configurations of the free edge surfaces thereof,may differ from what has here been shown.

I claim:

1. A deformable selflocking nut comprising an internally threaded innernut portion, an outer skirt portion surrounding said inner nut portionand generally coaxial therewith, said portions having an end adapted toengage a bearing surface and an end remote from the first said end, anda generally radial web portion integral with and interconnecting saidinner and outer portions at the end remote from the first said end, saidouter skirt portion extending axially beyond the inner nut portion atthe first said end, said inner portion including an enlargement adjacentthe first said end in contacting relation with the outer skirt portion,said radial web portion providing sufficient flexibility between the nutportion and skirt portion to permit relative movement therebetween, theouter skirt portion having an end surface which is adapted to engagesaid bearing surface, said end surface being tapered so that said endsurface has an inner periphery which projects beyond the outer peripheryof said end surface in the undeformed condition of the nut, the innernut portion having an end surface which is adapted to engage saidbearing surface, the latter said end surface being tapered so that saidlatter end surface has an inner periphery which projects beyond theouter periphery of said latter end surface in the undeformed conditionof the nut.

2. A nut as claimed in claim 1 wherein said web is continuous.

3. A deformable self-locking nut comprising an inner nut portion havinga threaded bore, an outer skirt portion surrounding said inner nutportion and generally coaxial therewith, said portions having free endsadapted to engage a bearing surface and a common end remote from saidfree ends, and a generally radial web portion integrally interconnectingand radially spacing apart said inner nut portion and said outer skirtportion at said common end, the free end of said outer skirt portionextending axially beyond the free end of said inner nut portion, saidnut portion having a radially enlarged solid mass extending for asubstantial distance from its free end toward said common end, the outersurface of said inner nut portion flaring from the region of said commonend outwardly in the region of said enlarged solid mass to and intocontact with the inner surface of said skirt portion at least at apurality of positions spaced around said nut portion and then extendingalong said inner surface of said skirt portion at each of said positionsto provide an area of frictional engagement between said nut and skirtportions in the area of said free end of said nut portion, said radialweb portion providing sufficient flexibility between the nut portion andskirt portion to permit relative movement therebetween.

4. A deformable self-locking nut comprising an inner nut portion havinga threaded bore and an outer skirt portion surrounding said inner nutportion and generally coaxial therewith, said portions having free endsadapted to engage a bearing surface and a common end at which they areintegrally joined, the free end of said outer skirt References CitedPortia extending axially beyond the free emf of said The followingreferences cited by the Examiner, are of inner portion the surface, fsaid f record in the patented file of this patent or the originalportion and the outer surface 0] stud inner nut portion patent being ineontact at at least a plurality of points spaced 5 UNITED STATES PATENTSaround said inner nut portion to provide areas of frictional 2 154 1744/1939 Marchou l51 2l engagement extending from a position adjacent saidfree 2287691 6/1947 Marchou l27 21 ends for at least a substantial axialdistance toward said 2:551:102 Delaney common end, the arrangement beingsuch that there is sufiicient flexibility between the nut portion andskirt 10 CARL T MLIN, Primary Examiner. portion to permit relativemovement tlterebetween. RAMON S, BRI'I'IS, Assi tant Examiner.

